It is well known that to attempt to capture the energy associated with flowing water, such as river currents or ocean tides, through the use of rotating members provided with vanes or paddles, great success in terms of efficiency can be achieved. For example, the hydroelectric complex at Niagara Falls is known to produce relatively low cost power in abundance. However, known high-efficiency applications generally demand that the flow of water be confined and caused to traverse through a sluice into a turbine, with deleterious impacts on the natural environment. Less environmentally-damaging mechanisms, such as river turbines, wherein the flow is not confined, have heretofore typically suffered from relatively poor efficiency.